A state is manufactured on purpose, and what a person manufactures before the battle decides what they can do inside it.
Voice, posture, and breath are levers a person can pull on command, and pulling them sets the state, and the state decides which emotion shows up to meet an army. Dread locks focus on the enemy's numbers; song aims it at Yahweh's character and puts words of certainty in a mouth that had been doing arithmetic.
Yahweh does the striking, and the rescue finds men already in motion. Not one of them felt like singing first; they sang, and the feeling came to meet the act. A person who waits to feel brave before acting brave hands every outcome to whatever mood they woke up in.